Explanations to understand some difficult concepts about boilers

Date published: 31 August 2012

Understanding the way a boiler works is not as difficult as it may seem at the beginning. The aim of this article is to make it easier for you to understand how a boiler works and to clarify some of the more difficult concepts to grasp. Understanding how a boiler works will allow you to make the right choice when you decide to buy a new boiler. Equally, if you have plumbing problems and you call a plumber to fix the problem, it will make the plumber’s explanations a lot clearer.

Definition

In spite of its name, water is not boiled inside a boiler. A boiler is indeed an appliance used to supply central heating and/or to provide hot water for taps and showers. The water is heated until the required temperature is achieved and then the heat source turns itself off.

What energy are boilers based on?

There are 4 types of fuel that can be used for a boiler:

- Solid fuel
- Electricity
- Gas
- Oil

Electric boilers are usually found in all-electric buildings such as blocks of flats, while solid fuel boilers are more labour intensive as they require loading up the fuel and emptying the ash. According to Treloar's “Master Basic Plumbing and Central Heating” (2010: p. 94), most boilers in the UK use gas, while the rest use oil. Treloar argues that it may be up to 92% of people in the UK use gas, while the rest use oil.

Types of Boiler Designs

1. Combination vs. System Boilers

A combination boiler has become the standard nowadays, due to their compact size. A combination boiler in contrast to a system boiler eliminates the need for storing hot water. Therefore, you will no longer need a hot water cylinder. A combination boiler will also allow you to save some money on hot water costs and will deliver water at the mains pressure. The flow however will be limited if several taps will be running at the same time. The only problem with combi boilers revolves around potentially the size of your house. If your house is too big, a boiler may not be sufficient to heat up the entire house. To complement this section, I also found this useful article about how combination boilers work.

System boilers, sometimes also called sealed system boilers, provide central heating through a storage cylinder. Therefore, a system boiler works on the principle of stored hot water. The hot water is pumped from the boiler through the system, which results in a fast and economical running. The benefit with system boilers is that they have the power to heat up bigger houses and in addition, they do not need feeds and expansion cistern.

TradePlumbing offers a great variety of both combi boilers and system boilers at affordable prices.

2. Condensing vs. Non-condensing boilers

A condensing boiler is also known as a high-efficiency boiler or a combi boiler and in contrast to non-condensing boilers, there is some consideration for heat, which is present in the combustion products and which are removed from the boiler. Condensing boilers are designed so that combustion products are cooled off and therefore, the heating energy of such products can be reused. These boilers can extract the extra heat by using the larger and more tightly grouped heat exchanger.

In contrast to boilers, which were installed 30 years ago and which operate at 50 or 60% efficiency, new boilers can operate at an efficiency of more the 90%. Essentially, boiler efficiency will have a direct impact on you gas bill. So, if your boiler is 50% efficient, that means that for every £100, you will only be getting £50 worth of heat, which means that the rest will be wasted up the chimney. In contrast, a boiler, which is 90% efficient, will allow you to get £90-worth of heat for every £100 that you spend. Nowadays, you would not even be able to install a boiler with an efficiency lower than 86%. The law requires that you install a boiler which has an efficiency of more than 86%.

3. Room-sealed vs. Open-flued

There are many different types of boiler designs, with subsidiary features and characteristics depending on the manufacturer. Boiler designs may feature natural or forced draught, which indicate the type of ventilation, which is used in order to get rid of the combustion products. If the boiler takes the air from within the room where the boiler is located, that will be an open-flued boiler. If the boiler takes the air from outside the building, that will be a room-sealed boiler.

These types of boilers are available:

- Natural draught room-sealed
- Forced draught room-sealed (fan-assisted)
- Natural draught open-flued
- Forced draught open-flued (fan assisted)

If you are not sure which type of boiler you have, there are two things to indicate whether you have an open-flued or room-flued boiler. A draught open-flued boiler will be usually placed in a kitchen, having a pipe emerging from the top, going to the chimney and going through a discharging pipe above the roof. If your boiler is placed behind a gas fire, then you are likely to have a draught open-flued boiler.

The list of criteria for distinguishing between boilers is not exhaustive, but it does help in understanding some of the more difficult concepts such as room-sealed vs. open-flued, condensing vs. non-condensing and combination vs. systems boilers. Of course, there are additional criteria to distinguish between boilers like size, capacity, or power. However, these are more straightforward concepts, which are easier to understand. To complement the information in this article, I also recommend this article on understanding your system from Energy Saving Trust.

Steps to keep your plumbing checks for winter

Date published: 28 August 2012

Winter is very unpredictable these days. While much snowfall and cold may put you in a holiday mood, they can also put a lot of strain on your home, due to potential boiler breakdown, burst pipes and expensive gas bills. In order to help you prepare for winter, we thought of creating a list of 5 steps to help you prepare your home for winter.

1. Check your central heating once a year
It is important to verify both your heating and cooking appliances once a year to ensure that they are working properly. The last thing you want is the central heating to stop working in winter. Therefore, in order to avoid that, we recommend you to get a Gas Safe registered engineer. In addition, you could check whether the radiators heat up yourself. You could run your central heating to maximum capacity and check whether radiators heat fully or not. If you notice some cold spots on the radiator, you may need to bleed your radiators. As far as bleeding radiators is concerned, we found this YouTube tutorial on how to bleed a radiator, useful.

2. Insulate your home
If you haven't insulated your house yet, you might want to consider doing that in the near future. Although you might have to spend a bit of money when you decide to insulate your home, it will be a good investment in the long-term. Not only will insulating your house keep the warmth inside for longer, but it will also save you some cash. Because you will be able to keep your house warm for an extended period, you will not have to turn the heating on as much; therefore, you will be able to lower your gas bills. According to this Directgov article on Insulation and Heating, insulating your loft would save you about £225 a year, while insulating your walls, could save you £110 a year on average. Furthermore, a good insulation together with an efficient boiler will also benefit the environment, by reducing carbon emissions.

3. Lag your pipes
Lagging entails wrapping a foam layer around your pipes to prevent them from freezing. Some of the areas, which are most at risk of freezing are the pipes in your loft, your garage and the area behind the boiler. In addition, it is worth knowing that both cold-water and hot-water pipes are equally likely to freeze if the hot-water pipes do not provide any heat to a room. In principle, you would need to follow these steps in order to make sure that you do manage to lag the pipes successfully:

- Check the pipe diameters
- Decide on the type of lagging tube that you want to purchase
- Push the tubes on to the pipes like a sleeve, making sure you secure the end of the pipes with a tape
- Make small v-shaped cuts in the tubing at the point where it corresponds to the bend in the pipe, to prevent ridges.

4. Repair dripping taps
Repairing any dripping taps will help prevent burst pipes in winter, caused by frozen water. The frozen water accrues in pipes and because of pressure, it can break the pipes and flood your house. Therefore, in order to prevent flooding, it is advisable that you fix any problems with potential dripping taps. I found this article on how to fix a dripping tap useful. In order to repair the dripping taps yourself, you will need the following tools: screwdrivers, slip-joint pliers, a spanner, a new washer and a piece of cloth.

5. Prepare your home if you plan to go away

- Drain your system by turning off the stopcock, running the taps and flushing the toilet until there is no water left
- Keep the temperature in your house constant to about 15 degrees
- Leave the loft trap door open – you will allow warm air to circulate and keep the pipes in the attic warm

6. Ask someone to check on your home once in a while

Wintertime is a great time for get-togethers, for seeing relatives and friends but it is also a great time for coming home to find water damage. If you plan to be away for more than a day, you should follow some easy steps that will prevent your plumbing from suffering from water damage.

To conclude, in order to make sure your house is prepared for winter, you should follow these steps: check your central heating, insulate your home, lag your pipes, repair dripping taps and prepare your house if you go away. This list of 5 steps is by no means exhaustive. However, we feel these would be the most important tips to follow if you want to enjoy the winter holidays, rather than spending time and money by calling plumbers in the middle of winter or even worse, repairing the damage caused by the different problems, which could emerge. Good luck!

Your hot water cylinder is designed to keep a ready supply of hot water for washing, showers and other household jobs. It holds a large volume of pre-heated water, ready for when you need it. Of course, water cools down over time. Even with insulation, your hot water cylinder will eventually cool down so that the water becomes tepid - not exactly ideal for baths and washing! To have an effective cylinder you need to have it kept at an optimal temperature. A cylinder thermostat is the clear choice for regulating the heating coil or element in your hot water cylinder.

A thermostat such as the Salus Cylinder/Pipe Thermostat is an economical high quality choice for fitting to your hot water cylinder.

View and Buy a Salus Cylinder Stat Here

You will probably be familiar with thermostats from central heating systems. These help maintain a steady temperature in the house by detecting the air temperature, and turning the heaters on and off depending on whether it is too hot or cold. The thermostat for your water cylinder works in much the same way. Instead of checking air temperature, it senses the water temperature at a certain point in the cylinder. When the water cools below the set temperature the thermostat turns on the element, bringing up the overall temperature. 

In practice you set the temperature at which you want the water to start re-heating, usually by turning a dial. The dials have a set of numbers around the edge - these are the temperatures; just match up the number for the temperature you want with the marker on the body of the thermostat. It's important to remember that the thermostat is really just an elaborate on/off switch - you can't affect the rate of heating by turning the dial up. That depends entirely on the efficiency and capacity of your cylinder heating element. 

A thermostat for a hot water cylinder is generally fitted to the body of the tank by a strap or band. This allows some degree of flexibility in the vertical positioning of the thermostat. The typical location is around one third of the way up the cylinder.

When installing a thermostat such as this cylinder stat, remember that fitting a thermostat will involve working with electrical wiring, so if you are not experienced it is best to hire a professional. Once properly installed a thermostat is typically long lasting and highly reliable.

Electric Only Towel Rails

An electric heated towel rail comes pre-filled with a liquid and has an electrical element as its only heat source.

Some electric towel rails come filled with oil and others come filled with a water-based solution containing a mix of central heating preservatives.  Here at Trade Plumbing we believe that a water-based solution is a far more environmentally friendly method.

Once the towel rail has been filled, bungs are then placed in the filling holes to keep the mixture in.  Another benefit of water-based thermal transfer fluid is that if there is some leakage during transportation it can be easily topped up with water. The electric towel warmers here at Trade Plumbing are filled with a mixture that is strong enough to be topped up around ten times during the lifetime of the product. To prevent damage during its journey to you we always pack the towel rail element separately in your box and would always recommend ensuring this is done. Your Part P registered Plumber or Electrician will be able to fit the element in your heated towel rail with ease.

Dual Fuel Towel Rails

A Dual Fuel towel rail comes with no filling fluid as it is plumbed in to your central heating system allowing it to be heated by your central heating system; it also has an electrical element so it can still be used when your central heating system is not active.

In summer, most Brits switch off their central heating system. This means that the towel radiator will not warm up and dry your towels after that morning bathroom rush.  The way to keep the benefits of a heated towel rail during summer months without wasting electricity when your central heating system is being used is to fit an electric element to the towel rail, as well as have it plumbed in to the central heating circuit.  This is generally achieved by using what are called T pieces - these make it possible to run the electric element and the radiator valve onto the towel rail.

When adding a radiator or towel rail to a circuit, we recommend that you add a tube of Central Heating protector, which will help to keep the water in your central heating circuit in tiptop condition and help to prevent boiler breakdowns and corrosion of your radiators.

At Trade Plumbing as the vast majority* of our centrally  heated  towel rails can be used as Dual Fuel systems we  ask you to  choose  your towel rail from our extensive range  of centrally heated  towel  rails and then upgrade using our simple Dual Fuel Kits.

Additional Information and Recommendations for Electric and Dual Fuel Towel Rails for Bathrooms

At Trade Plumbing we recommend you install a Timer for your towel rail, so you can automate it to switch on and be ready just in time for when you need it; this helps your towel rail become more convenient as well as economical and environmentally friendly.

You will need a Fused Spur and Back Box for your towel rail if you have an electrical element. In laments terms this is a big electric switch for the wall. This is fitted to your normal domestic ring main.

So finally, you just need to decide whether you need a standard element or a digitally-controlled thermostatic element:  

Single Heat

This type of element has just one active setting ‘on’ or ‘off’. This means the purchase price is lower than those in the thermostatic range. With no heat controls this type of towel rail can become HOT to the touch. This type of element gives you all the luxury of an electric heated towel rail at an affordable price.

Thermostatic

This type of element has thermostatic controls, so can be set to a temperature of your choice. This control system has a number of benefits including safety (especially for children) and energy conservation, potentially resulting in cheaper running costs. The temperature can be selected between 30 - 60°C in 7.5°C intervals. The MEG element comes complete with indicating LED lights and easy to use controls. This type of element gives you everything you need in terms of style and effectiveness while giving you continued piece of mind

*For a list of Towel Rails that cannot be used with Dual Fuel kits please click here

Roll top baths - all you need to know

What is a roll top bath? - Roll top baths - all you need to know 

When you think of style and luxury, and an image that sums up these characteristics in your home, the bathroom is perhaps the ultimate symbol of opulence. Much more than just a functional room that you walk into dirty and walk out clean, the bathroom is your haven in which to relax, unwind and take time to simply forget about the world.In here, the wolrd's problems are a million miles away. And in your bolthole away from the noise and stress of modern life, nothing symbolises relaxation and comfort more than your bath tub. Roll top bathspresent an image of style and luxury that is unrivalled in bathroom suites. So called because of the curved edges at the top of the frame, these free standing tubs are the archetypal image of a luxury bath. Cool and modern yet with a very traditional style, the “rolled” top offers greater comfort as you soak away your worries. This can also reduce the risk of injury that can come from getting in and out of the bath. The free standing design is a nod to the earliest bath tubs, and also serves to eliminate the risk of mould collecting around the base. Many modern tubs are made from acrylic as a means of reducing cost and offering a more contemporary, minimalist design. These can still be quite beautiful and are a wonderful focal point for your bathroom. For the ultimate in style, or for a very traditional look, you can also find copper roll top baths that provide the ultimate image of Victorian luxury. Enamelled metals like cast iron are also a great option. As an extension of the roll top design, slipper baths also commonly feature the rolled edges and offer an even greater level of comfort. Slipper baths are designed with one deeper side, allowing you to recline almost fully in the tub. The name comes from the higher wall on one side giving a slipper shape, and once you settle in for a hot soak in one of these you will realise how apt the name is; like the comfort of your favourite winter pair! For those that are environmentally conscious (or simply like sharing a bath), both can be designed with central taps to allow for two. In the case of slipper baths, both ends offer the same reclining shape. When it comes to choosing the bath for you, there are various factors to consider. The balance of style, luxury and of course cost is all important in making your dream bathroom. Whether you choose to go for a cool, modern roll top bath, or a luxurious slipper bath, there are a multitude of designs out there to suit every taste. We recommend that you take a look at the leg packs for your Free Standing Bath.

Leg packs and Tap pipes for Free Standing Baths. Choose from a wide range of Bath Taps suitable for Roll Top Baths and Slipper Baths.

Having hot water readily available in a house is an important contributory factor in creating a good standard of living for the occupants. Fortunately for the UK, the majority of its houses contain either a combination boiler, or a hot water tank or cylinder that distributes hot water around the home, once it has been heated by a boiler or other device.

Two common types of water cylinders are ‘direct’ and ‘indirect’. A direct cylinder stores water and heats it with an internal electric immersion heater. The most commonly implemented heating system, used in new houses, actually uses an indirect cylinder. In an indirect system a copper coil filled with hot water from the boiler passes through the inside of the cylinder. This heats the water inside it indirectly because no hot water from the boiler ever mixes with the water in the cylinder. The storage capacity of both cylinders allows them to provide hot water for several appliances simultaneously. This gives you the useful ability to wash up while someone else is enjoying a warm shower. A variation on the single coil cylinder is a twin coil cylinder. This uses two coils to heat a cylinder indirectly. There are several alternative ways to heat the water that passes through the copper coil, other than a gas burning system: solar panels and wood-burning stoves are common examples of these. A twin coil cylinder combines an environmentally-friendly system and a standard boiler to heat the water in the main cylinder indirectly. Using two coils means you can operate a more eco-friendly source and top up the heat where necessary with your gas or oil boiler. 

Both direct and indirect water cylinders can be vented or unvented. Unvented means that the cylinder uses the mains water pressure to push the water through to the outlets. A vented cylinder uses a tank in your loft to provide the water pressure needed to supply the water to your taps. If your heating systems utilise a solid fuel, such as wood or coal, then a vented cylinder is compulsory because you are unable to precisely control the heat going from the boiler to the cylinder. A vented cylinder will allow for any excess heat and pressure to be released through the header tank because it is unsealed.

When shopping for a cylinder there are many factors to consider. The most important thing is to consider all of the possible configurations and to find what makes the most sense to you, in terms of money and sustainability. Nobody likes being without the basic comfort of hot water so a sensible investment is recommended. We recommend you consult a professional installer before you buy. Check out the following sections of our website for the types of cylinder available.

Unvented Cylinder Pressurised Cylinders

Vented Hot Water Cylinder

Direct Hot Water Cylinders

Indirect Hot Water Cylinders

5 Steps explained

Choosing and buying a new radiator might not be such a difficult task in its essence as long as you kept in mind some important ideas like:

• The radiators should have at least a 2-year guarantee.
• They should be pressure-tested to 152.3 PSI (10.5 bar) in order to be able to handle a pressure of 116 PSI (8 bar) at a temperature of 95°C.
• The output of the radiator should comply with the  BSEN442 European standard for radiators.

If you do not resort to a specialist’s help, here are some tips that you should take into account when replacing an old radiator and that can be quite easily implemented. Connecting a radiator to an already existing central heating system is a pretty straightforward DIY job that can be conducted in a matter of hours.

The aim of this article is to provide a tutorial on how to fit in a new radiator yourself without the help of a professional plumber. I will provide some tips on how to choose the location of the radiator, on how to remove the old radiator (if applicable), how to fit the new radiator to the wall, some tips concerning how to cut a pipe, how to connect the new radiator and finally, how to deal with corrosion.

1. Location of the radiator

If you are not replacing an old radiator and you just want to add a new one to the system, you must probably be already aware that radiators are usually placed where the draft enters the house, somewhere near a window or near the entrance door. Now you should be aware that there are problems with both locations; for instance, if you place a radiator near a window, the length of the curtains could have a negative effect on the way heat is distributed inside your home.

Also, the location of the radiator near the entrance door might pose some problems in case you have disabled persons or children in your family. Derived from the curtain problem, you should make sure consequently that you leave enough room for the heat to circulate and for the valves to be installed. The distance between that base of the radiator and the ground should be of approximately 150 mm, at least.

*Note: depending on the type of radiator, you should leave a specific distance between the wall and the radiator as well:
- 40-46 mm for single panel
- 58-65 mm for double panel
- 35-44 mm for single convector radiators
- 60-71 mm for double panel plus
- 71-84mm for double convector.

Another factor that should influence your decision to place the radiator somewhere is the position of the pipe. You should be aware that there are two types of pipes – flow and return. Older system might just have one pipe playing the double role.

In a single pipe system, there is a flow pipe that takes the heated water from the boiler while the return pipe brings the water to the boiler to be heated again. In twin pipe system, you should first try and fix the radiator tails (screw fitting that should come with a lock shield or  thermostatic radiator valves).

Before screwing it to the radiator, you should put some PTFE tape around the thread in order to improve the quality of joints seals. The tails could be quite easily tightened with a radiator spanner.

2. Removing the old radiator (if applicable)

If you are not replacing an old radiator, you can skip this section. If you are replacing a radiator however, there is some advice that you should take into account:

• Switch off the central heating. If you have conventional heating though, you should stop the cold water from coming to the tank or tie the ball valve so that refilling is not permitted. Another exception is a conventional vented system, in which case you will have to take the water out from the system before physically removing the radiator.
• Drain off the water from the radiator: (1) You should open the square with a suitable spanner (2) Make sure you have a hose pipe connected to the draincock Type A (see picture below) for a sealed system to deal with leaking water. In a conventional vented system, you could use a hosepipe and clamp it on with a jubilee clip and then try and reach the other point of the hose pipe. (3) Remove all the water in the radiator so that you make sure the water is not going to ruin your house as well.
• Undo the bleed valve from the radiator so that the water can drain off from the system.
• When the radiator is empty, you can start undoing one of the valves at the bottom of the radiator; you will probably still notice some water leaking, so you will still have to go and drain some water downstairs. It may be necessary that you should take the water out of the whole system.
• Remove the fittings and lift it upwards in order to remove it from the brackets.

3. Fitting the radiator to the Wall

Once you have decided on the location of the new radiator, you will probably want to fix it to the wall. In order to do that, you have to follow 5 easy steps:

• Measuring the distance between two fastening points on the back of the radiator.
• Drawing a vertical line on the wall employing a bubble level (spirit level).
• Drawing an additional line to correct the distance apart.
• Fastening the brackets to the wall.
• Putting the radiator on to the brackets.

4. Cutting the pipe (better done by plumber)

You need a pipe slice for copper pipes and plastic pipe slicers for plastic.

• Place a bowl under the pipe since some residual water is likely to come out.
• In order to place the ‘T’ fitting, you need to cut more from one of the pipes.
• Make sure you have push-fit fittings and compression fittings at hand.
• In case you’re working with copper pipes, have a pipe bender and a pipe bending spring at hand.
• After inserting the ‘T’ fitting, run the pipe from the flow and return pipes to the new radiator (the flow pipe should have the valve on).

5. Connecting the new radiator

Once all the above things were observed, you can finally connect the new radiator:

• Connect the radiator making sure that the pipe inserts are used.
• In case you are using compression valves, you should have copper olives since other types of valves may be too hard for plastic pipes.
• Close the drain off valve.
• Remove the hosepipe.
• Close the bleeding valve from the radiator that you might have opened previously.
• Fill the system again using the cold supply filling loop and if it is a vented system via the water supply system i.e. loft water supply tank.
• Check new fittings for potential leakages (in case you come across any leakages, tighten the screws or make sure that the pipes are pushed all the way into the fitting).
• After doing everything, you should bleed the radiator. You can view our previous article, called  How to bleed your radiator in order to get the right information on how to do it.

How to deal with Corrosion

Most people worry about corrosion when installing a new radiator. This is indeed something that you should consider which is inevitable in its essence. What you can do is to prolong the need to replace the radiator. 
Which are the factors that affect corrosion?

• The type of metal employed in the system
• The amount of air drawn into the system
• The type of water that gets into the system
• The quality of the work for the radiator installation.

What can be done to prevent early corrosion of your radiator? 
Some things you need to do when installing the new radiator:

• Proper water flushing and filling after the radiator had been installed.
• Application of some  corrosion inhibitors, in accordance with the manufacturer’s instructions.

Conclusion

In a nut-shell, don’t forget:

• In terms of  location, make sure that you leave enough room for the heat to circulate and for the valves to be installed.
• When you  remove the radiator, drain the system out.
• Fix the radiator to the wall.
• Cut the pipe (if necessary).
• Connect the new radiator.
• Use some  corrosion inhibitors.

Good Luck!

Understanding bath thicknesses

Common questions about the thickness of your new bath answered

When purchasing a new bath you will find that they come in two thicknesses - 5mmand 8mm, so it makes sense that when your new bath arrives it should measureeither 5mm or 8mm in thickness, right?
Wrong, in fact, you will find that your new bath does not measure either thickness.Confusing we know, but this is not the manufacturer, or indeed supplier misleadingyou, it is a result of the bath manufacturing process, and is one of the most commoncustomer queries dealt with by bathroom supply stores nationwide.

To clear up this common misconception, here's an explanation of whathappens in the making of your new bath.

Firstly, it is important to understand that when measuring the thickness of a bath, youshould not measure the base. On any vacuum-formed product, like a bath, the basewill always be thinner than the top rim. Similar to blowing up a balloon, the more airyou introduce the thinner the rubber will become.

1. A piece of acrylic (5mm and 8mm) is placed in a hot oven for a period of time so itbecomes soft and malleable.
2. When removed from the oven it is clamped on to a frame and an aluminium bathtool is pushed up into it so the acrylic stretches. As the acrylic is pushed the edgesbecome thinner and it is only the section that remains clamped to the frame thatremain 5mm or 8mm in thickness. This section will eventually be the trimmed edgeof the bath, i.e. where your panel will meet the bath edge.
3. A vacuum pump is then turned on and the air is sucked out of the aluminium toolcausing the soft acrylic to be drawn down in the bath shape, and gradually becomethinner as it is pulled into the base.
4. Once the acrylic sheet has cooled and stiffened the vacuum is turned off and theclamping frame removed.
5. The bath will later need to be reinforced so that it is suitable for its intendedpurpose.

So, the important points to remember from this process are:• The acrylic remains 5mm or 8mm where it has been clamped, althoughit will be trimmed slightly to 4 - 4.5mm and 6.5 - 7mm respectively beforepacking• The acrylic is thinner in the section that has been lifted• The acrylic is gradually thinner as it is pulled down into the base - thedeeper the bath the thinner the base and sides will be

Now you know the facts, identifying a 5mm or 8mm bath will be relatively easy.Remember, you cannot measure a bath by the depth of its plughole or the thicknessof its sides or base.